1. Field of the Invention
This invention relates to a television signal kind discriminating apparatus suitable to distinguish between a MUSE (Multiple Sub-Nyquist Sampling Encode) signal which is a form of a transmission signal of high definition television and a popular television signal.
2. Description of the Related Art
It sometimes occurs that one of BS NTSC broadcasting and MUSE broadcasting is alternatively transmitted on a single channel such as BS broadcasting. The two transmission systems are quite different in processing of both of an image and sound from each other. Accordingly, it is necessary to discriminate a kind of a received signal to change over the processing or muting of either or both and sound.
In a conventional television signal kind discriminating apparatus, whether or not a received signal is a MUSE signal is discriminated by detecting frame pulses which are a reference signal for each frame inserted in a MUSE signal. In the discriminating process of the conventional television signal kind discriminating apparatus, detection of frame pulses over a plurality of frames based on a flywheel effect is performed by taking a detection error of the frame pulses which is caused by noise or by some other factor into consideration.
If muting of sound is performed by the conventional television signal kind discriminating apparatus in accordance with a result of the discriminating method described above, then when an input television signal is changed over from a MUSE signal to an NTSC signal, noise is produced problematically for the time of 1/30.times.n seconds (n is a number of frames for detection of frame pulses based on a flywheel effect).